--> A New Generation of Digital Maps Showing Potential Petroleum Habitats in New Zealand's Offshore North-Western Province (Reinga-Northland-Taranaki Basins)

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A New Generation of Digital Maps Showing Potential Petroleum Habitats in New Zealand's Offshore North-Western Province (Reinga-Northland-Taranaki Basins)

Abstract

The distribution of petroleum systems elements such as source, reservoir, and seal rocks, provides key input to understanding basin prospectivity. The NZ Government-funded “Atlas of Petroleum Prospectivity” programme is producing a GIS-based series of updated digital maps and metadata of these key geological components to help understand the potential for petroleum accumulation in New Zealand's northwestern petroleum province (greater Taranaki, Northland and Reinga basins). The digital maps represent a collation of both existing, and new interpretation of regional data based on seismic character of reflection packages, isopach maps, lithologies and depositional settings and biostratigraphic analysis from wells. These digital maps, including new paleogeographic maps, are the main inputs for common risk segment (CRS) maps of source, reservoir and seal rock presence in the northwestern province. The most likely source rocks throughout the northwestern province are Late Cretaceous coaly rocks, with proven oily source rock potential in the Taranaki Basin. Older Cretaceous units may also have source potential, including foreset facies, pro-delta marine shales, and early syn-rift non-marine deposits. Jurassic coals may be an important source rock in Reinga-Northland basin. Late Paleocene marine shales may also have source potential, although the distribution of source facies and their maturity are poorly known. Potential reservoir units are widespread Late Cretaceous non- to shallow-marine sandstones. Paleocene–Eocene transgressive sands are proven reservoirs in Taranaki Basin and may also have good reservoir potential in the Deepwater Taranaki and Reinga-Northland basins. Older, mid to Late Cretaceous syn-rift deposits in Deepwater Taranaki may have reservoir potential, but are poorly understood. Triassic–Early Cretaceous rocks also contain potential reservoirs in Reinga-Northland, but their reservoir quality is likely to be poor. Submarine fan systems of Late Cretaceous to Miocene age may have reservoir potential, but their distribution and reservoir quality are poorly constrained. One exception are Late Eocene fans, which has some potential in northern Taranaki and Northland basins. Seals are well developed throughout the region, in the form of Late Cretaceous–Eocene marine mudstones as well as Miocene-Pliocene marine shales. Oligocene–earliest Miocene marls are likely to have particularly good sealing properties.